Busybox replacement

From eLinux.org
Revision as of 17:07, 22 January 2012 by Landley (talk | contribs) (Add in SUSv4 section, and commands.)
Jump to: navigation, search

This page has information about the commands and features desired for a busybox replacement program.

See Busybox replacement project for the project proposal for this work.

Command List

We have several potential use cases for a busybox replacement, and are using those to determine a consensus on which commands to target for a 1.0 release of an unencumbered busybox replacement package.

Our current candidate list combines the commands toybox already implements, the development environment command list, the toolbox standard commands, the Sony configuration of busybox, and the selected subset of the SUSv4 standard.

Thus the first release of a busybox replacement should include the following commands:

 at awk basename bc bunzip2 bzcat bzip2 cal cat catv chgrp chmod
 chown chroot chvt cksum cmp comm count cp cpio csplit cut date dd df
 diff dirname dmesg dnsdomainname du echo egrep env expand expr
 false fgrep file find fold freeramdisk ftpd ftpget ftpput fuser
 getconf getty grep gunzip gzip halt hd head help hostname id
 ifconfig iftop init insmod install ioctl ionice join kill
 killall klogd less link ln logger login logname losetup ls lsmod
 lsof man md5sum mdev mkdir mkfifo mknod mkswap mktemp modprobe
 more mount mountpoint mv nc netcat netstat newgrp newfs_msdos 
 nice nl nohup notify od oneit paste patch pathchk pgrep pidof
 ping ping6 pivot_root pkill poweroff printenv printf ps pwd
 readlink reboot renice rm rmdir rmmod route sed seq setsid
 sfdisk sh sha1sum sleep sort split start stat stop stty swapoff
 swapon switch_root sync syslogd tabs tac tail tar taskset tee
 telnet telnetd test time top touch tput tr true truncate tty
 umount uname unexpand uniq unlink unshare uptime usleep uudecode
 uuencode vconfig vi vmstat wc wget which who whoami xargs yes

Plus additional to-be-determined shell functionality.

Toybox currently implements

The triaged toybox (2 clause BSD license) is currently implementing usable versions of:

 bzcat cal cat catv chroot chvt cksum count cp df dirname dmesg
 echo false help link mkswap nc netcat nice nohup oneit patch pwd
 rmdir seq setsid sha1sum sleep sort sync tee true truncate tty
 uname unlink unshare wc which yes

And contains partial implementations of:

 mdev sh

See the Toybox todo list for the most up to date status.

Use case: provide a self-hosting development environment

The following commands are enough to build the Aboriginal Linux development environment, boot it to a shell prompt, and build Linux From Scratch 6.8 under it. (Aboriginal Linux currently uses BusyBox for this, thus provides a corresponding test environment for toybox.)

This use case includes running init scripts and other shell scripts, running configure, make, and install in each package, and providing basic command line facilities such as a text editor. (It does not include a compiler toolchain or C library, those are outside the scope of this project.)

Already in toybox

 bzcat cat cp dirname echo patch rmdir sha1sum sleep sort sync
 true uname wc which yes env

Additional commands for development environment

 zcat awk basename bzip2 chmod chown cmp cut date dd diff
 egrep expr find grep gzip head hostname id install ln ls
 mkdir mktemp mv od readlink rm sed sh tail tar touch tr uniq
 wget whoami xargs chgrp comm gunzip less logname man split
 tee test time bunzip2 chgrp chroot comm cpio dmesg
 dnsdomainname ftpd ftpget ftpput gunzip ifconfig init less
 logname losetup man mdev mount mountpoint nc pgrep pkill 
 pwd route split stat switch_root tac tee test time umount vi

Note: Aboriginal Linux installs bash 2.05b as #!/bin/sh and its scripts require bash extensions not present in busybox ash.

Use case: replacing Toolbox commands

Standard commands

Toolbox in Android (what version?) implements the following standard commands:

date id uptime ifconfig start stop newfs_msdos
ls route netstat ioctl reboot cmp insmod chmod
cat lsmod chown df top printenv ionice rmmod
sleep notify iftop rmdir dd vmstat hd rm mount
ln lsof ps dmesg renice kill mkdir mv
sync umount

Android-specific commands

Toolbox also provides the following nonstandard commands, which are unique to Android (or at least do not appear in Ubuntu or SUSv4):

 alarm schedtop getprop log setprop watchprops notify wipe
 getevent sendevent nandread smd setconsole r ioctl

Busybox commands

default 1.10 build

A default build of Busybox 1.10 has the following commands:

	[, [[, addgroup, adduser, adjtimex, ar, arp, arping, ash,
	awk, basename, bunzip2, bzcat, bzip2, cal, cat, catv,
	chattr, chgrp, chmod, chown, chpasswd, chpst, chroot,
	chrt, chvt, cksum, clear, cmp, comm, cp, cpio, crond,
	crontab, cryptpw, cut, date, dc, dd, deallocvt, delgroup,
	deluser, df, dhcprelay, diff, dirname, dmesg, dos2unix,
	du, dumpkmap, dumpleases, echo, ed, egrep, eject, env,
	envdir, envuidgid, expand, expr, false, fbset, fdflush,
	fdformat, fdisk, fgrep, find, fold, free, freeramdisk,
	fsck, fsck.minix, fuser, getopt, getty, grep, gunzip,
	gzip, halt, hdparm, head, hexdump, hostid, hostname, hwclock,
	id, ifconfig, ifdown, ifup, inetd, init, insmod, install,
	ip, ipaddr, ipcalc, ipcrm, ipcs, iplink, iproute, iprule,
	iptunnel, kbd_mode, kill, killall, killall5, klogd, last,
	length, less, linux32, linux64, linuxrc, ln, loadfont,
	loadkmap, logger, login, logname, logread, losetup, lpd,
	lpq, lpr, ls, lsattr, lsmod, lzmacat, makedevs, md5sum,
	mdev, mesg, microcom, mkdir, mkfifo, mkfs.minix, mknod,
	mkswap, mktemp, modprobe, more, mount, mountpoint, mt,
	mv, nameif, netstat, nice, nmeter, nohup, nslookup, od,
	openvt, passwd, patch, pgrep, pidof, ping, pipe_progress,
	pivot_root, pkill, poweroff, printenv, printf, ps, pscan,
	pwd, raidautorun, rdate, readlink, readprofile, realpath,
	reboot, renice, reset, resize, rm, rmdir, rmmod, route,
	rpm, rpm2cpio, run-parts, runlevel, runsv, runsvdir, rx,
	script, sed, sendmail, seq, setarch, setconsole, setkeycodes,
	setlogcons, setsid, setuidgid, sh, sha1sum, sleep, softlimit,
	sort, split, start-stop-daemon, stat, strings, stty, su,
	sulogin, sum, sv, svlogd, swapoff, swapon, switch_root,
	sync, sysctl, syslogd, tac, tail, tar, taskset, tee, telnetd,
	test, time, top, touch, tr, true, tty, ttysize, udhcpc,
	udhcpd, umount, uname, uncompress, unexpand, uniq, unix2dos,
	unlzma, unzip, uptime, usleep, uudecode, uuencode, vi,
	vlock, watch, watchdog, wc, wget, which, who, whoami,
	xargs, yes, zcat

Sony CE Linux (internal distribution) 1.13.4 build

This is from a version of busybox used in lots of Sony products: Currently defined functions:

        [, [[, ash, basename, bunzip2, bzcat, cat, chgrp, chmod, chown,
        chroot, cmp, cp, cpio, cut, date, dd, dirname, dmesg, echo, egrep,
        env, expr, false, fgrep, freeramdisk, ftpget, ftpput, getty, grep,
        gunzip, gzip, halt, ifconfig, insmod, kill, killall, klogd, ln,
        logger, login, ls, lsmod, md5sum, mkdir, mkfifo, mknod, mktemp,
        modprobe, mount, mv, pidof, ping, ping6, pivot_root, poweroff,
        pwd, readlink, reboot, rm, rmdir, rmmod, route, sed, sfdisk, sh,
        sha1sum, sleep, sort, stty, swapoff, swapon, switch_root, sync,
        syslogd, tail, tar, taskset, telnet, telnetd, test, touch, true,
        umount, uname, uniq, usleep, vconfig, wc, xargs, zcat


The best standards are the kind that describe reality, rather than attempting to impose a new one. (I.E. a good standard should document, not legislate.)

The kind of standards which describe existing reality tend to be approved by more than one standards body, such ANSI and ISO both approving C. That's why the IEEE POSIX committee's 2008 standard, the Single Unix Specification version 4, and the Open Group Base Specification edition 7 are all the same standard from three sources.

The [http://opengroup.org/onlinepubs/9699919799/idx/utilities.html "utilities" section] these standards is devoted to the unix command line, and are the best such standard for our purposes. (BusyBox was implemented with regard to SUSv3, an earlier version of this standard.)

Problems with the standard

Unfortunately, these standards describe a subset of reality, lacking any mention of commands such as init, login, or mount required to actually boot a system. It provides ipcrm and ipcs, but not ipcmk, so you can use System V IPC resources but not create them.

These standards also contain a large number of commands that are inappropriate for toybox to implement in its 1.0 release. (Perhaps some of these could be reintroduced in later releases, but not now.)

Starting with the full "utilities" list, we first remove generally obsolete commands (compess ed ex pr uncompress uccp uustat uux), commands for the pre-CVS "SCCS" source control system (admin delta get prs rmdel sact sccs unget val what), fortran support (asa fort77), and batch processing support (batch qalter qdel qhold qmove qmsg qrerun qrls qselect qsig qstat qsub).

Some commands are for a compiler toolchain (ar c99 cflow ctags cxref getcat iconv lex m4 make nm strings strip tsort yacc), which is outside of toybox's mandate and should be supplied externally. (Again, some of these may be revisited later, but not for toybox 1.0.)

Some commands are part of a command shell, and cannot be implemented as separate executables (alias bg cd command fc fg getopts hash jobs kill read type ulimit umask unalias wait). These may be revisited as part of a built-in toybox shell, but are not exported into $PATH via symlinks. (If you fork a child process and have it "cd" then exit, you've accomplished nothing.)

A few other commands are judgement calls, providing command-line internationalization support (iconv locale localedef), System V inter-process communication (ipcrm ipcs), and cross-tty communication from the minicomputer days (talk mesg write). The "pax" utility was supplanted by tar, "mailx" is a command line email client, and "lp" submits files for printing to... what exactly? (cups?) The standard defines crontab but not crond.

Removing all of that leaves the following commands, which toybox should implement:

 at awk basename bc cal cat chgrp chmod chown cksum cmp comm cp
 csplit cut date dd df diff dirname du echo env expand expr false file find
 fold fuser getconf grep head id join kill link ln logger logname ls man
 mkdir mkfifo more mv newgrp nice nl nohup od paste patch pathchk printf ps
 pwd renice rm rmdir sed sh sleep sort split stty tabs tail tee test time
 touch tput tr true tty uname unexpand uniq unlink uudecode uuencode vi wc
 who xargs zcat

Random Notes

Can implement incrementally

Rob wrote:

One nice thing about busybox/toybox/toolbox is you can install multiple implementations side by side, and have what symlinks you create (or what comes first in the $PATH) determine who is implementing what.

This allows gradual transitions. Each release, we replace a couple more commands from the old one, until the old one finally isn't being used for anything anymore and we can uninstall it...